I have a 1997 Ranger 4.0 extended cab 4x4 and when I put the truck into four wheel drive it will engage and then make a loud popping sound or like a large thud when I pull out. I can feel it when it makes the noise like it is slipping and popping back in. I took the truck up to Gatlingburg,TN up some steep mountains in the snow, and it would work and then all of a sudden a loud boom in the front end...Any suggestions???I just bought this truck off a guy in Kentucky who never took this truck off road......

make sure that you are a complete stop when shifting in and out of four wheel drive, i know they say that you can shift on the fly but it is the safest way to switch into 4x4, and your hubs may be disengaging late, ford automatic locking hubs aren't that reliable, i suggest getting manual locking hubs, you would have to get out the vehicle to lock them in every time, but it is the most reliable way so you won't get stranded because the hub won't engage